Japanese Patent Laid-open Application No. H1-214388 (hereinafter referred to as “Patent 1”) discloses therein a trim length adjusting structure for a conventional hair cutter. In the conventional example described in Patent 1, a cutter block consisting of a stationary and movable blade, both of which are comb-shaped and one of which reciprocates, is protrudingly disposed at one end portion of a main body. A cylindrical comb attachment in a comb shape for trim length adjustment is movably engaged at the portion of the main body where the cutter block is disposed and along the projected direction of the cutter block. An elastic hook provided at the rear portion of the comb attachment is engaged with an annular groove provided at the front end of a cylindrical adjustment element which is rotatably and movably disposed around the main body. A protrusion projecting on the exterior surface of the main body is inserted into a spiral groove formed on the inner circumferential surface of the cylindrical adjustment element. By rotating the cylindrical adjustment element, the adjustment element is moved in the longitudinal direction while it rotates around the main body along the spiral groove. As a result, the comb attachment in a comb shape is movable in the projected direction of the cutter block.
Further, hair or beard brought in from the base portion of the comb attachment comes in contact with the stationary blade in a comb shape and then is cut by the movable blade at a desired cutting length. In this case, the cutting length can be adjusted by rotating the adjustment element.
However, in the conventional example above, since the cylindrical comb attachment is merely movably engaged with the main body, it rattles in an approximately perpendicular direction to its movable direction, thereby making a rattling noise while interfering the trimmer's handling quality. Further, also in the area where the protrusion on the main body's exterior surface is inserted in the spiral groove, the cylindrical adjustment element rattles and makes a similar noise. In this case, in order to eliminate such rattling, if the comb attachment and the main body are made to engage tightly, or otherwise, the spiral groove and the protrusion on the main body's exterior surface are tightly fitted, the friction between the parts would increase, so that precise operation of the cutter becomes more difficult. Further, in order to mass produce the cutter with features with such subtle dimensional variations, maintaining the product quality becomes a formidable challenge.